Title: Spiral ~Suiri no Kizuna~ (volume 2)
Media: Manga (tankouban)
Story: Shirodaira Kyo
Art: Mizuno Eita
Publisher: Gangan Comics (a Square/Enix publication)
Volume two of Spiral picks up right where the first left off, with the locked room mystery. As I read through, I keep meaning to go back and look at the similarities and differences between the manga and anime adaptation, since I know there are a couple of changes between the two (primarily to keep the number of incidental knifings down in the anime, is my assumption).
Ayumu quickly proves himself in the finale of the locked room saga, unmasking the culprit with a certain Holmesian flare.
Speaking of differences between the anime and the manga, it was interesting to see, between reading the first two volumes, and watching the first two episodes of the anime, what got left out when the series got animated. Really, the anime truncated the manga storyline, and attached it at different points, involving the same people in multiple events rather than using the original manga characters in order to tighten up the time frame.
Anyway, after the locked room comes what is, in my opinion, the first point in Spiral where I said to myself, "I have to see the rest of this.": The turtle bomb. I know, if you haven't read or watched Spiral, your mental image here probably isn't capturing the event. Essentially, Ayumu has half an hour to somehow decipher a nine-digit disarm code, or the concert hall he was in will be blown to bits (and him with it, of course). Now, you can solve the disarm code yourself, with the right information (and a bit of luck). Just consider what a turtle from China, and a three-by-three grid have in common. The last piece you need is that the number 1 (one) is in the second box of the third column.